← Open problems
MUB-10.10
For d = p1^n1 ... pr^nr not a prime power, is a set of min_i (p_i^n_i + 1) nice MU bases strongly unextendible?
In plain terms
Related to Conjecture 6.2, confirmed for d <= 15.
Our position — ours alone, not the authors'
A conjecture verified to d <= 15 is a bounded finite check with an obvious next value. The classic compute-overhang profile -- verified this far because that is where someone stopped, not where the mathematics stopped (LESSONS R5). Cheap to gate.
Desk gate — required before any core-hours
- find what bounded d=16..20 and whether it was hardware or theory
Source
Daniel McNulty, Stefan Weigert, Mutually Unbiased Bases in Composite Dimensions -- A Review
Quantum 10, 2051 (2026) · §10.3
https://doi.org/10.22331/q-2026-04-01-2051
Licence:
CC-BY-4.0
— the problem statement is quoted here under that
licence, with attribution, and has not been modified